In turbine engines, compressed air discharged from a compressor section and fuel introduced from a source of fuel are mixed together and burned in a combustion section, creating combustion products defining hot combustion gases. The combustion gases are directed through a hot gas path in a turbine section, where they expand to provide rotation of a turbine rotor. The turbine rotor is linked to a shaft to power the compressor section and may be linked to an electric generator to produce electricity.
Combustion produces pressure oscillations within the combustion section, which cause combustion dynamics in the form of acoustic waves. These waves may lead to flame instability, and vibrations that match the natural resonance frequency of one or more engine components can ultimately cause fatigue or wear failure in combustor components. Damping devices such as resonator boxes may be used to suppress or absorb acoustic energy generated during engine operation to keep acoustic oscillations within an acceptable range. Because cooling requirements and space limitations often restrict the ability to damp combustion dynamics, particularly low and intermediate frequency dynamics, fuel staging is often used to mitigate combustion dynamics, which often requires a level of non-homogeneity in the mixture. However, these strategies frequently lead to undesirable pollutant emissions and may limit combustor performance. Mitigation of combustion dynamics is further complicated by the fact that a single component may have multiple natural frequencies, and the resonance frequencies of engine components may change over time.